Difference between non-woven and woven geotextiles
Geotextiles are geosynthetic materials with several applications in civil engineering. These robust synthetic fabrics are manufactured for multiple uses like soil stabilization, erosion control, construction, drainage and many such geotechnical projects. They are typically manufactured from either polypropylene or polyester. The most common types of geotextiles are woven and non-woven fabric.
What is a woven geotextile?
Woven geotextiles are produced when single yarns are woven together in a loom. This yields tough and durable geo-fabrics that are used for roadways, driveways, residential streets, and highway applications. Although it’s less porous than other types, woven geotextiles serve long-term separation and reinforcement needs. Its corrosion resistance ensures durability in even adverse chemical environments.
What are the functions of woven geotextiles?
- Reinforcement: Woven geotextiles use their high tensile strength to reinforce soil. They absorb tensile forces, improving the soil’s shear strength and overall stability. This allows for steeper slopes, stronger foundations, or thinner road bases.
- Separation: Another feature of woven geotextiles is material separation. For instance, a woven geotextile can be used in a landfill to separate the waste from the soil underneath.
- High load support: Woven geotextiles, due to their high tensile strength, enhance the load-bearing capacity of soil structures. In applications like roads under heavy traffic, they reinforce the pavement layers, help distribute loads more effectively onto the subgrade, and reduce deformation.
- Permeability: Woven geotextiles are valued for their high tensile strength, making them excellent for soil reinforcement and contributing to structural stability. They are permeable materials, allowing water to pass through, which can be crucial for applications like relieving pore water pressure.
- Tensile strength: Tensile strength refers to the maximum tensile force that a geotextile can withstand without breaking. A geotextile with high tensile strength is essential for effectively supporting mechanical loads, ensuring stability and durability in construction projects. Understanding the tensile strength of a geotextile helps in selecting the appropriate material for specific engineering needs.
Applications of woven geotextiles
Woven geotextiles are a material of choice for its three inherent material properties which are mechanical, chemical and physical in nature. These material features make geotextiles a preferred choice to use in a number of industries –where construction needs to be optimized.
- Highways: Woven geotextiles are used to reinforce the base of paved roads and highways, preventing it from shifting or settling under heavy traffic loads. By separating the road base from the subgrade, they enhance the integrity and lifespan of the pavement. They also prevent erosion on road slopes and embankments and assist with drainage, reducing water accumulation that can cause rutting, pore pressure build-up, and structural deformation. Additionally, they filter fine particles, preventing soil migration from the subgrade.
- Parking lots: Parking lots withstand repetitive and localized loading, as well as extreme temperature variations. Woven geotextiles are used to reduce reflective cracking, minimize pothole development, and improve pavement performance. When deployed correctly, between layers of the subgrade, they can reduce settlement by up to 30% and extend the lifespan of parking lots by 5–7 years by reinforcing the pavement and limiting interaction with the subgrade.
- Basal reinforcement for embankment over soft soil: Woven geotextiles improve the distribution of loads applied to the embankment structure reducing the excessive settlement or failure of the soft soils. This creates an even distribution of loads over a larger area, thus minimizing the local stress concentrations that otherwise lead to deformation. By improving tensile strength, the woven geotextiles enhance the shear resistance by acting as a reinforcement layer and prevent sliding or slumping.
- Load Transfer Platforms (LTP): Woven geotextiles are used in design and construction of load transfer platforms. When installed in LTP, woven geotextiles creates lateral and vertical reinforcement, thereby limiting soil movement. It also creates a stiffening effect that resists the compression of the granular layers above it. Furthermore, the separation function prevents the degradation of the granular fill, preventing soil clogging and internal erosion.
What is a non-woven geotextile?
Non-woven geotextiles are manufactured by needling the fibres, among other mechanical entangling forms. They are mainly made from synthetic polymers, including polyester and polypropylene, and their strength is improved mostly through heat treatment, making them highly permeable. Non-woven geotextiles are often used in projects for protection, filtration, separation, and drainage.
What are the functions of the non-woven geotextiles?
- Filtration: Non-woven geotextiles perform well when it comes to filtration processes. They allow fluid to pass through a porous structure while retaining solids and contaminants, making them useful in water filtration, wastewater treatment, and soil erosion control.
- Separation: Non-woven geotextiles excel at separation, which means preventing two distinct soil or aggregate layers from mixing. By keeping these layers separate the geotextile ensures each material maintains its intended structural integrity and function over time. This prevents issues like the subgrade contaminating the base course, thereby preserving the road’s strength. In applications like landfills, non-woven geotextiles separate different layers within the liner or cap system and often protect the primary impermeable barrier from damage, rather than acting as the impermeable barrier themselves.
- Drainage: The porous nature of non-woven geotextiles facilitates drainage. They are indispensable act as drainage to regions lacking good soil conditions and excessive moisture. Such materials are frequently used in landscaping, construction, and agriculture.
- Permeability: Outstanding permeability is among the critical effective properties in describing non-woven geotextiles. This immediately conveys that fluid can pass directly through such fabric.
- Weight classification: Non-woven geotextiles are generally classified by weight per unit area. It is important to consider in selecting geotextiles for an application, as weight will affect a whole host of other things, including, but not limited to, strength and permeability for a given fabric.
Applications of non-woven geotextiles
- Under rock riprap revetments: Non-woven geotextiles are also placed under rock riprap revetments, acting as a filter to hold the soil in position and prevent it from clogging the voids between the rocks due to soil washing. This protects the revetment structure, keeping soil erosion beneath the revetment at bay.
- Enveloping French drains: Unbonded geotextiles are most commonly used to envelop french drains. This protects against the drain getting clogged by filtering soil particles, increases drainage for water flow with a smoother path for the movement of water, and prevents possible erosion around the drain.
- Alternative subsurface drainage solutions: Non-woven geotextiles make sense as an option for replacing drainage networks, such as perforated pipes and wick drains, in a subsurface drainage system. This will prevent drainage systems from clogging, increase the flow of water through the systems, and aid in preventing erosion around them.
How is a non-woven geotextile different from a woven geotextile?
- Application: Woven geotextiles are primarily used for reinforcement and stabilization that is caused by their high tensile strength and durability. They are particularly suitable for roadways and embankments, where structural integrity is necessary. On the other hand, non-woven geotextiles, filtration, separation and drainage are better suited for applications. Their high permeability makes them ideal for water filtration, waste water treatment and landfill liner.
- Manufacturing: Woven geotextiles is produced using a loom that weaves individual yarn in a structured fabric. This method gives them a more defined structure and more tensile strength. Non-woven geotextiles are manufactured by bonding using techniques like needle-punching or heat treatment. It is suitable for a low -structured but more permeable fabric, fluid movement and filtration.
- Properties: Woven geotextiles are known for their high load-bearing capacity and tensile strength, making them ideal for applications requiring tough and durable materials. Non-woven geotextiles are generally more porous, allowing higher water flow-through rates. This makes them more effective for filtration and drainage tasks. In contrast, the tighter structure of woven fabrics limits permeability but increases mechanical strength.
- Materials: Both woven and non-woven geotextiles are typically made from durable polymers, primarily polypropylene or polyester. The choice of material is based on specific project requirements and affects properties like chemical resistance (e.g., to high or low pH), creep behavior under long-term load, UV stability during installation, and overall performance.
In summary, woven and non-woven geotextiles are engineered with distinct characteristics that suit different applications. Woven geotextiles excel in reinforcement and stabilization, whereas non-woven geotextiles are ideal for filtration, separation, and drainage.